Any mail app works. When asked, choose IMAP and use these settings (also shown on your site's Email tab):
Username: your full address (hello@example.com) Password: the mailbox password Incoming: IMAP · box.masterpc.co.uk · port 993 · SSL/TLS Outgoing: SMTP · box.masterpc.co.uk · port 587 · STARTTLS
iPhone / iPad
Settings → Mail → Accounts → Add Account → Other → Add Mail Account. Enter address + password; if it doesn't auto-detect, fill the servers above.
Android (Gmail app)
Gmail → Settings → Add account → Other. Enter the address, pick Personal (IMAP), then the servers above.
Outlook / Thunderbird
Add account → type the address → choose IMAP when prompted → servers above.
Sending fails but receiving works? Double-check the outgoing port is 587 with authentication ON — same username and password as incoming.